High-frequency lamination of polymer foams

ABSTRACT

Olefin interpolymers having carbon monoxide polymerized as a comonomer therein are found to be useful as an HF-bondable layer between various substrates, including, e.g., a foam layer and a surface layer, whereby laminated foams are obtained.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional, of application Ser. No. 738,006, filed May 28,1985 now U.S. Pat. No. 4,671,992, which is a continuation-in-part ofco-pending Ser. No. 645,990 filed Aug. 31, 1984, U.S. Pat. No. 4,601,948which is, itself, a continuation-in-part of copending application Ser.No. 531,110 filed Sept. 12, 1983 U.S. Pat. No. 4,600,614.

FIELD OF THE INVENTION

Laminated polymer foams, such as upholstery.

BACKGROUND OF THE INVENTION

The use of high-frequency electromagnetic energy as a means for heatingpolymers is an advancing art which finds application in many fields,especially in fields in which conventional conductive, convective, orradiant heat energy is either not suitable, not practical, or notpossible. For instance, sealing of a polymer to itself or to some othersubstrate can be (if the composition of the polymer is appropriate) animportant commercial technique in producing a desired end-product.

There are some polymers which are not suitable, or at least notwell-suited, for high-frequency heating operations. In such ill-suitedpolymers high-frequency heating either does not occur, or if it occursit does so only after inefficiently prolonged periods of treatment time.In production assembly lines, e.g., a quick heat-seal operation isgenerally preferred over a prolonged heat-seal operation.

Among the polymers which are ill-suited for high-frequency heating areolefin polymers, e.g., polymers and copolymers of ethylene, propylene,styrene or other α-olefinically unsaturated hydrocarbons having about 2to about 10 carbon atoms. Some of these olefin polymers may containpolar groups, or polarizable groups, due to the incorporation thereinof, e.g., acrylic (or methacrylic) acids or their alkyl esters ascomonomers with the olefins, and these groups may, at high levels ofincorporation tend to impart a modicum of high-frequency heatability tothe polymer, but the efficacy is generally so slight that it isinfeasible on a commercial basis. Some polymers having polar groups,e.g. chlorinated P.E., ethylene/vinyl acetate copolymer, PVC,polyvinylidene chloride, and polyamide, are heatable under the influenceof certain frequencies of electromagnetic radiation, but are notgenerally well-suited for bonding using the higher frequencies.

Polyethylene is particularly known in the art to be substantiallyunsuitable for high-frequency heating unless sensitizers are added tothe polymer; this is true regardless of whether it is linear orbranched, or of whether it is low, medium, or high density (see, e.g.,U.S. Pat. Nos. 3,336,173; 3,640,913; and 3,810,799).

It is an object of the present invention to provide a bonding film whichhas high-frequency heatability in order to bond a surface layer ofmaterial to a polymer foam substrate by the use of high frequencyelectromagnetic radiation.

SUMMARY OF THE INVENTION

Surface materials are laminated to a polymer foam substrate by employinga bonding film between said surface material and said polymer foam, saidbonding film being HF-sealable. The bonding film is preferably a carbonmonoxide-containing interpolymer.

DETAILED DESCRIPTIONS

The preparation of olefin polymers, copolymers, and terpolymers is wellknown and the methods and techniques are well known to practitioners ofthe relevant polymer art. For the most part, the olefin copolymers andterpolymers of interest in this present disclosure are prepared by thewell known high pressure, high temperature, free-radical initiated,polymerization method such as the historically-popular ICI process orsuch as disclosed in U.S. Pat. No. 2,497,323. However, thosepolymerization processes which employ certain of the coordinationcatalysts or metal catalysts (e.g., the well-known Ziegler-type,Natta-type, or Phillips-type) may be used in selecting a catalyst (suchas in U.S. Pat. No. 3,083,184) which is not easily poisoned ordeactivated by carbon monoxide, or other oxygen-containing monomer,which is generally highly reactive with many metal-carbon bonds.

Olefin polymers within the purview of this invention, and which arerendered heatable (by high-frequency electromagnetic radiation) byincorporating carbon monoxide groups into the polymer chain, arepolymers formed by polymerizing monomers having ethylenic (olefinic)unsaturation. A sole olefin or a plurality of olefins may be used alongwith the carbon monoxide in preparing the polymers. Preferably theolefin monomer is ethylene (sometimes including a small proportion of aC₃ -C₈ aliphatic olefin for property modification). The olefin monomercan also include an unsaturated organic acid having 3 to 8 carbon atoms,such as acrylic acid, methacrylic acid, 1-butenoic acid, and the like;alkyl esters or metal salts of these acids may also be used, such asethyl acrylate, methyl methacrylate, 2-ethyl hexyl acrylate, sodiumacrylate, potassium methacrylate, and the like. HydrogenatedCO-containing olefin polymers (which creates H--C--OH groups along thepolymer chain) are included here, such as hydrogenated ethylene/carbonmonoxide copolymers. U.S. Pat. No. 2,495,292 discloses methods ofhydrogenating such CO groups in a polymer chain.

It has been known for many years that olefins, e.g. ethylene, and carbonmonoxide, can be copolymerized or terpolymerized.

The following listed patents are believed to be representative of theart pertaining to interpolymers of carbon monoxide and monoolefins: U.S.Pat. Nos. 2,495,292; 2,495,286; 2,497,323; 2,641,590; 3,083,184;3,248,359; 3,530,109; 3,676,401; 3,689,460; 3,694,412; 3,780,140;3,835,123; 3,929,727; 3,948,832; 3,948,873; 3,948,850; 3,968,082;3,984,388; 4,024,104; 4,024,325; 4,024,326; 4,139,522; 4,143,096; and4,304,887; and Canadian 471,169.

It is also known that there are additives (sensitizers) which can beblended into a polymer, e.g. polyethylene, to render it heatable byelectromagnetic high-frequency energy, such as talc, ZnCl₂, carbonblack, nylon, iron oxide, and others. Such additives, however, usuallyhave a pronounced visual, physical, or chemical effect which, in someapplications, is desirably avoided. Furthermore, when using additives assensitizers one is faced with having to obtain a uniform distribution ofthe sensitizers in order to avoid "hot-spots" or arcing which can giveirregular results and may even damage the polymer or other parts of thelaminate.

It is within the purview of one aspect of the present inventive conceptto create high-frequency sensitizer groups along the polymer chain inpolymers which otherwise would be ill-suited for high-frequency heating.In this invention one does not encounter untoward visual effects in thepolymer as a result of the sensitizer. Even in the present embodimentswherein a polymer of the present invention is blended with polymer(e.g., as a "masterbatch") in order to sensitize the whole, the polymersare generally compatible to an extent at which little or no visualeffects are encountered. Thus, clear films of olefin polymers can beprepared, in accordance with the present invention, which are readilyheat-sealed using high-frequency (HF) energy. It is especially ofimportance that the present invention provides polymers which areheatable by the action of microwave (MW) energy, a particular portion ofthe high-frequency energy range, thereby helping to fill a need in theindustry where there is a sparsity of polymers which are suitable. Theamount of CO groups in the ethylene interpolymers should be in the rangeof about 0.1 to about 50% by weight, preferably about 1 to about 40% byweight, most preferably about 5 to about 30% by weight.

As used herein "high-frequency sealability" refers to the bonding of thesealable polymer to a portion of itself or to another material usingelectromagnetic energy frequencies of 0.01-30,000 MHz. This includesradio-frequency (RF) heating and microwave (MW) heating incontradistinction to conventional heat sealing. The high-frequency rangeis generally taken to include electromagnetic waves over a broadfrequency range (0.01 to 30,000 MHz) and covers the ultrasonic frequencyrange (18 KHz-1000 KHz), the radio frequency (RF) range (1 MHz-300 MHz),and the microwave (MW) frequency range (300 MHz-10,000 MHz). The RF andMW ranges are of particular interest here, with special interest in theMW range due to the increasing use of MW as a processing device.

Uses for this technology (polymer or blends) includes packagingapplications were high speed and/or non-destructive seals are required,e.g., high-frequency activated adhesive films; extrusion coatings;moldings; hot melts in uses such as aseptic packaging, retort pouches,sandwich bags; lamination of foam, fabric, or film layers; powdermoldings, and the like. Furthermore, the present invention providespolymers suitable for use in RF extruders, including continuousextruders or batch extruders. Wire and cable coatings can be applied ina continuous RF-extruder by the present invention.

In one aspect, this invention relates to an improved method of renderinga polymer which is not heatable or sealable utilizing high-frequency(0.1-30,000 MHz) electromagnetic radiation (HF) (e.g., polyethylene,polypropylene, polystyrene, etc.) HF-sealable by either incorporation ofcarbon monoxide by copolymerization or by blending or grafting a carbonmonoxide copolymer or terpolymer into the polymer matrix. Hydrogenatedforms of the above can also be used. In addition, ethylene/carbonmonoxide copolymer (ECO) and interpolymers containing CO can be used formicrowave sealing applications (i.e., microwave sealable plastic bags,toothpaste tube sealing, shampoo tube sealing, other microwave sealablecontainers, valve bag sealing, etc.). We have unexpectedly found thatECO copolymers and interpolymers convert high-frequency electromagneticradiation into heat for sealing, welding or fusing over a broadfrequency range (0.1-30,000 MHz). Typically, ethylene copolymers may beheatable to some extent at low RF frequencies of 1-50 MHz (radiofrequency range is typically considered to be from 1-300 MHz; microwavefrequency range is 300-30,000 MHz) such as ethylene/vinyl acetatecopolymer (EVA), but none have been found which efficiently heat at thehigher frequencies. Other examples of polymers heatable at lowfrequencies, but which do not efficiently heat at the higher frequenciesare polyvinyl chloride (PVC), polyvinylidene chloride (PVDC),chlorinated polyethylene (CPE), and Nylon 6.

The advantages of sealing polymers with high-frequency electromagneticwaves include faster and more efficient sealing, sealing through poorheat-conductors, e.g., paper or cardboard exteriors, stronger seals orbonds, improved economics based on efficient use of energy input, theability to seal, bond, or laminate larger surface areas, sealing ofthicker or more complex film laminates and specific sealing.

The general heating rate for the interaction of an electromagnetic wavecan be used to determine sealing rates utilizing the following equation:

    G=13.3×10.sup.-14 fF.sup.2 (E' tan δ)          (1)

where G is the heating rate in cal/cm³.sec, f is the frequency in Hz ofthe electromagnetic wave, F² is the field strength or power in volts/cm,E' is the dielectric constant of the polymer and tan δ is the dielectricloss tangent (measure of the heating property of the material whenexposed to HF electromagnetic waves). Thus, in general (since tan δvaries with frequency) the higher the frequency the higher the heatingrate or the faster the sealing ability of the material. The carbonmonoxide (CO) containing interpolymers can be sealed or heated over abroad frequency range which allows one to have the option of usingmicrowave frequencies for optimum speed in heating or sealing. Thisfeature (heating or sealing over such a broad frequency) appears to beunique to these interpolymers or copolymers containing CO.

There are also advantages of CO copolymers or interpolymers over otherpolymers (e.g., PVC, PVDC, CPE, EVA), that are sealable using radiofrequency sealing methods which include, for example:

1. ECO is like conventional low density polyethylenes in physicalproperties and film appearance, i.e., higher melting point, low filmblockage, easy processability, can be used for film, extrusion coatingand molding resin. Furthermore, the need for plasticizers is obviated.

2. CO can be copolymerized with ethylene and vinyl acetate to produce aCO-modified EVA polymer to render it more sealable and broadens thesealing frequency range. CO can also be copolymerized into an EAA orEMAA polymer allowing an EAA-like or EMAA-like terpolymer to be RF andmicrowave sealable (EAA and EMAA are not RF or microwave sealable). Thisincludes the metal salts or "ionomer-type" embodiments of thesepolymers.

3. CO containing polymers or interpolymers have higher dielectricconstants than EVA copolymers, allowing higher field strengths to beused without the fear of arcing.

EXAMPLE 1

The following Table I shows the time required to melt a polymer in amicrowave oven (Sears Microclassic microwave oven) at maximum power(brought 275 ml of water to boil in 2.48 minutes).

                  TABLE I                                                         ______________________________________                                                                   Melt Time                                          Resin*            MI***    (sec)**                                            ______________________________________                                        ECO                                                                           10% CO            1        37                                                 10% CO            10       35                                                 5% AA; 10% CO     10       75                                                 5% AA; 10% CO     3.5      85                                                 5% AA; 5% CO      3        90                                                 1% CO             1        90                                                 EVA (14% VA)      wax      >10 min                                            EAA (12% AA)      wax      >10 min                                            Oxidized (PE)     wax      >10 min                                            E/vinyl alcohol   --       42                                                 EVA/CO (20% CO)   --       25                                                 EVA                                                                           28% VA            3.5      >10 min                                            18% VA            3.0      >10 min                                            EVA                                                                           20% AA            300      >10 min                                            30% AA            1250     >10 min                                            HDPE (0.965 dens.)                                                                              .8       >10 min                                            LDPE (0.918 dens.)                                                                              6        >10 min                                            LLDPE (0.918 dens.)                                                                             6        >10 min                                            6 resin (dried)   --       >10 min                                            Saran ® B-2000 polymer                                                                      --       >10 min                                            Chlorinated P.E. (CPE)                                                                          --       >10 min                                            ______________________________________                                         *Samples were 2" (5.08 cm) diameter discs of 60 mil (1.5 mm) thickness,       positioned on a nonRF sensitive polycarbonate sheet.                          **If no melting was evident in 10 minutes, the test was stopped and           reported as >10 min.                                                          ***MI is melt index in accordance with ASTM D1238.                            ® Registered tradenames                                              

As can be seen from Table I, only ethylene/vinyl alcohol polymer andethylene interpolymers containing carbon monoxide melted in themicrowave oven (2450 MHz).

EXAMPLE 2

In order to determine the RF-sealability of carbon monoxide containingcopolymers, a Callanan 11/2 KW high-frequency electronic generatorequipped with a 3/32"×12" (0.24×30.5 cm) brass sealing electrode andoperating over a frequency range of 20-40 MHz (RF) was utilized in thefollowing sealing experiment. Samples of 3-mil blown film of thecopolymers shown in Table II were attempted to be sealed using the aboveRF sealer utilizing various dwell settings (sealing time) and powersettings. The seals were examined and a seal was considered to have beenmade when the two sheets of material could not be separated at the sealpoint without tearing either piece of film. Table II also shows theimprovement in minimum sealing time and resistance to arcing of COcontaining copolymers in comparison to EVA copolymers.

                  TABLE II                                                        ______________________________________                                        RADIO FREQUENCY SEALABILITY                                                               Power     Dwell Time                                              Resin       Setting   sec.       Sealability                                  ______________________________________                                        EVA         90        3          No                                           (9.3% VA, 2 MI)                                                                           100       3          No                                                       100       4          Arc*                                         EVA         10        1          No                                           (18% VA, 2.5 MI)                                                                          40        2          No                                                       70        2          Yes                                                      60        2          Yes                                                      70        1          No                                                       80        1          Yes                                                      90        2          Arc                                          EVA         60        2          No                                           (12.0% VA, 2.5 MI)                                                                        70        2          No                                                       80        2          No                                                       90        2          Yes                                                      100       1          Arc                                          EVA         30        2          Yes                                          (25% VA, 2 MI)                                                                            20        2          No                                                       60        1          Yes                                                      60        .5         No                                                       70        .5         No                                                       80        .5         Arc                                          EVA         40        2          Yes                                          (28% VA, 3.0 MI)                                                                          20        1          Yes                                                      70        .5         Yes                                                      80        .25        Arc                                                      80        .5         Arc                                          ECO         50        2          No                                           (10% CO, 1 MI)                                                                            60        2          No                                                       70        2          Yes                                                      100       1          Yes                                                      90        1          Yes                                                      80        1          No                                                       100       .5         Yes                                                      90        .5         No                                           E/AA/CO     70        2          Yes                                          (5% AA, 10% CO,                                                                           60        2          Yes                                          3.5 MI)     50        2          Yes                                                      70        1          Yes                                                      60        1          Yes                                                      70        .5         Yes                                                      60        .5         No                                                       80        .25        No                                                       90        .25        Yes                                          E/AA/CO     70        .5         Yes                                          (5% AA, 10% CO,                                                                           80        .5         Yes                                          10 MI)      80        .25        No                                                       90        .25        Yes                                          ______________________________________                                         *Arc results in a hole burned through the film.                          

Within the purview of the present invention, useful articles areprepared which utilize the high-frequency electromagnetic radiationheatability and sealability of the above described CO containing olefinpolymers. Layers or plies of these polymers are used as a means forsealing or bonding materials which are not, themselves, efficientlysuitable for high-frequency electromagnetic radiation sealing orbonding. Various substrates, including particles, films, sheets, blocks.rods, spheres, and the like can be coated, at least in the area desiredto be bonded, with these subject polymers and then sealed or bondedtogether using high-frequency electromagnetic radiation, especiallythose frequencies in the microwave range. These polymers, in the form ofpowders or particles, may be extruded into useful shapes, or as coatingsonto other materials (e.g. wire and cable coatings), usinghigh-frequency electromagnetic radiation as the heating means.

Novel adhesives comprising terpolymers of ethylene/carbonmonoxide/carboxylic acid are prepared as embodiments in accordance withthe present invention. The carboxylic acid moiety of the terpolymer maybe any of the unsaturated carboxylic acid which are polymerizablethrough the double-bond, such as acrylic acid, methacrylic acid,crotonic acid, 1-butenoic acid, and the like, especially acrylic acid ormethacrylic acid, most especially acrylic acid, including salts of theseacids, such as metal salts, especially Na or K salts, commonly known as"ionomer" salts. The preparation of these E/CO/acid terpolymers may bedone in the same manner as the E/acid copolymers as disclosed in U.S.Pat. Nos. 3,520,861 and 4,351,931. These patents disclose the use of ahigh pressure stirred autoclave reactor, using a free-radical initiator,to prepare uniform, random ethylene/carboxylic acid copolymers. Whereasthese terpolymers can also be made by grafting techniques, by blockpolymerization techniques, in batch reactors, or in long tube reactors,it is preferred that the above disclosed stirring autoclave reactors beused whereby substantially uniform, random terpolymers are made.

Even though E/AA copolymers are generally regarded as having goodadhesive properties with many substrates, as compared to polyethylene,there are some substrates where improved adhesion is desirable. Notableamong these substrates, where improved adhesion is desirable, arepolyamides (e.g. nylons), polyolefins (e.g. LDPE, HDPE, LLDPE, PP, OPP,polyisoprene), fluoropolymers (e.g. PTFE), polyethylene terephthalate(PET), metals (e.g. steel and aluminum foil), some paper-type products(e.g. glassine, kraft paper, etc.), cured epoxy resins, ethylene/vinylalcohol copolymers, cured novolac resins, polyurethanes, polycarbonates,chloropolymers (e.g. polychloroprene, PVC, polyvinylidene chloride, andinorganic substrates (e.g. glass and porcelain).

Conversely, whereas ECO copolymers exhibit a modicum of heat-activatedor heat-induced adhesive properties to some substrates, it has beendetermined that the present E/CO/acid terpolymers exhibit greateradhesiveness in such instances, especially to such substrates as SARANpolymer and polycarbonate (where ECO has some adhesiveness) and toethylene/vinyl alcohol copolymers, nylon, and aluminum (where ECOexhibits little or no adhesiveness).

The adhesive properties of these E/CO/acid terpolymers may be utilizedby any convenient method, such as by hot-melt application, bypost-heating of the adhesive in-situ on the substrate, by application ofthe adhesive in a carrier, such as in a solvent or as a dispersion in anaqueous carrier or in a non-solvent. The adhesive may be used in joiningsubstrates of similar or dissimilar materials. As mentionedhereinbefore, these terpolymers are also suitable for use as films or asother materials and have the beneficial property of being high-frequencyheatable, especially at those frequencies which are in, or near, themicrowave range.

These E/CO/acid terpolymers are quite similar in optics and physicalproperties to EAA copolymers made by the same process. Insofar as thesenovel adhesive terpolymers are concerned, the ranges of the comonomeringredients are as follows:

    ______________________________________                                        Weight % of Terpolymer                                                                                          Most                                        Monomer      Operable    Preferred                                                                              Preferred                                   ______________________________________                                        Ethylene     20-98       40-98    60-96                                       Carbon Monoxide                                                                            1-40        1-30     2-20                                        Carboxylic Acid                                                                            1-40        1-30     2-20                                        ______________________________________                                    

The melt index (M.I.), also called melt flow rate, as measured inaccordance with ASTM D-1238, is preferably in the range of about 0.5 toabout 2500, most preferably in the range of about 1 to about 60, evenmore preferably in the range of about 1 to 20.

These E/CO/acid terpolymers are thermoplastic and can be thermoformedinto films, sheets, tubes, or other articles. Powders of theseterpolymers can be compression molded into sintered forms or the powderscan be applied to the surface of a substrate where it can beheat-plastified to provide an adhesive layer or coating on the substrateor between two substrates. A film, strip, or sheet of these terpolymerscan be placed between two substrates and heat-plastified to serve as anadhesive or laminate layer to hold the substrates together.

The following examples illustrate certain embodiments of the E/CO/acidterpolymers, compared with other polymers, but the invention is notlimited to the specific embodiments shown.

EXAMPLE 3

The examples shown in Table III below are produced by compressionmolding at pressures and temperatures conducive to heat fusion. Theresin samples to by tested for adhesion are first compression moldedinto 20 mil (0.51 mm) plaques and then laminated to the substrate (afilm or plaque) to test for adhesion to the substrate. The adhesive ofethylene/carbon monoxide/acrylic acid terpolymers, E/CO/AA, is shown incomparision to low density polyethylene, LDPE; ethylene/acrylic acidcopolymer; E/AA; ethylene/vinylacetate copolymer, E/VA; ethylene/carbonmonoxide copolymer, E/CO; and ethylene/carbon monoxide/vinyl acetateterpolymer, E/CO/VA. The good adhesiveness obtainable with E/CO/AAterpolymers to the various substrates is evident, especially with nylon(a polyamide) and with polycarbonate which generally do not form strongbonds with most heat-plastified adhesives.

                                      TABLE III                                   __________________________________________________________________________    COMPRESSION MOLDED ADHESION VALUES (lbs/in)                                               PERCENT COMONOMER                                                             WITH ETHYLENE     SUBSTRATE                                       ADHESIVE    AA  CO   VA   MI  A.sup.1                                                                            B.sup.2                                                                           Nylon.sup.3                                                                        Aluminum.sup.4                                                                      EVAL.sup.5                                                                         Polycarbonate.sup.6    __________________________________________________________________________    LDPE        --  --   --   --  .01  .01 .01  .05   .01  .01                    E/AA Copolymer                                                                            6.2 --   --   3.02                                                                              .01  .02 2.4  18.1  .50  .05                    E/AA Copolymer                                                                            9.8 --   --   9.6 .01  .01 3.8  29.2  .70  .08                    E/AA Copolymer                                                                            9.0 --   --   3.6 .01  .01 4.2  27.4  .50  .08                    E/VA Copolymer                                                                            --  --   28.5 5.8 7.5  6.3 5.4  2.1   3.1  .08                    E/VA Copolymer                                                                            --  --    6.5 1.11                                                                              .04  .10 6.44 8.9   6.8  .05                    E/CO/AA Terpolymer                                                                        5.0  5.0 --   56.1                                                                              >10.47                                                                             >2.39                                                                             1.83 18.0  3.1  7.5                    E/CO/AA Terpolymer                                                                        5.0 10.0 --   4.3 11.8 >1.89                                                                             9.88 16.0  7.5  >10.4                  E/CO/AA Terpolymer                                                                        5.0 10.0 --   18.7                                                                              9.0  >4.2                                                                              >23.2                                                                              22.5  7.9  >10.4                  E/CO Copolymer                                                                            0   10.0 --   7   9.6  >2.4                                                                              .5   .4    .2   >7.8                   E/CO Copolymer                                                                            0   10.0 --   8.2 10.3 >4.1                                                                              .1   .8    .5   >8.2                   E/CO/AA Terpolymer                                                                        10.0                                                                               5.0 --   4.1 7.1  1.5 >24.2                                                                              24.9  6.9  DNR                    E/CO/VA Terpolymer                                                                        --  10.0 10.0 35.2                                                                              8.2  6.1 8.8  2.0   1.33 DNR                    __________________________________________________________________________     > indicates cohesive failure strength of film substrate                       A.sup.1 6mil (0.15 mm) SARAN PVDC film                                        B.sup.2 2mil (0.051 mm) SARAN PVDC film                                       .sup.3 Nylon-6 film                                                           .sup.4 Aluminum                                                               .sup.5 ethylene/vinyl alcohol copolymer, molded 20mil (0.51 mm) plaque        .sup.6 2-mil (0.051 mm) polycarbonate cast film                          

EXAMPLE 4

In order to compare an ethylene/carbon monoxide copolymer (10% CO byweight, 18.7 M.I.) with an ethylene/carbon monoxide/acrylic acidterpolymer (10% CO and 5% AA by weight, 12.8 M.I.), a 2-mil (0.05 mm)thick coating of each is extrusion-coated onto various substrates andadhesion (lb./in.) is measured. In Table IV below, Sample A is the E/COcopolymer and is extrusion-coated at about 300° C.; Sample B is theE/CO/AA terpolymer and is extrusion-coated at about 290° C.; PVDC meanspolyvinylidene chloride; EVAL means ethylene/vinyl alcohol copolymer;LLDPE means linear low density polyethylene; LDPE means low densitypolyethylene; PET means polyethylene terephthalate; OPP means orientedpolypropylene. (1 lb./in.=175 N/m)

                                      TABLE IV                                    __________________________________________________________________________    SAMPLE                                                                              PVDC                                                                              PET                                                                              POLYAMIDE                                                                             OPP ALUMINUM                                                                              LDPE                                                                              LLDPE                                    __________________________________________________________________________    A     >5* 0.5                                                                              0.32    <0.05                                                                             0.14    0.3 0.07                                     B     >5* 1.6                                                                              2.44    0.05                                                                              2.5     0.5 0.5                                      __________________________________________________________________________     *All ">" samples resulted in film failure, not adhesive failure. The abov     illustrates the superior adhesiveness of E/CO/AA terpolymers as compared      to E/CO copolymers.                                                      

EXAMPLE 5

The packaging industry utilizes a number of barrier resins, such as inTable V below, and the E/CO/acid terpolymers are found to make goodadhesives for making laminates which contain one or more barrier layers.

                  TABLE V                                                         ______________________________________                                        Oxygen Barrier Resistance                                                     Nominal Value*                                                                           Polymer                                                            ______________________________________                                        0.03-0.30  ethylene/vinyl alcohol copolymers; EVAL                            0.05-0.20  polymers or copolymers based on vinyl                                         chloride and/or vinylidene chloride                                           monomers; SARAN polymers                                            2         polyvinyl chloride, PVC                                            80         plasticized PVC                                                     4         PET, polyethylene terephthalate                                    10         nylon, polyamide                                                   125        HDPE, high density polyethylene                                    ______________________________________                                         *cc of O.sub.2 as measured by ASTM D1434                                 

EXAMPLE 6

It has been determined that E/CO/acid terpolymers are useful asheat-plastified adhesives between layers of similar plastics or resins,layers of dissimilar plastics or resins, and/or between layers ofplastics or resins and completely different substrates, such as paper,cloth, metal, glass, vitreous material, wood, leather. These terpolymersare also useful as heat-plastified adhesives between layers ofmaterials, neither layer being plastic or resin, such as the materialsnamed immediately above.

Certain embodiments of this invention relate to fabric/foam laminatedstructures in which a dielectrically or radio frequency (RF) sealablepolyolefin film is used as an adhesive film to laminate, e.g., a clothfabric cover to a polyurethane flexible foam. A polyolefin film whichhas a dielectric loss index greater than 0.2 (e.g., ethylene/acrylicacid/carbon monoxide, ethylene/carbon monoxide, or ethylene/vinylacetate interpolymers, etc.) is inserted between a polyurethane flexiblefoam and a cloth fabric cover. The entire composite structure is thensimultaneously laminated and embossed using a dielectric or RF sealer.This invention and structure alleviates the need to utilize specialdielectrically heatable polyurethane foam formulations which requirespecial machines for their production, are more expensive, and haveinferior properties due to the addition of the dielectrically heatablematerial (e.g., PVC powder, metal filings, polyesters, etc.) Thisinvention also allows fabrics or other cover materials to be laminatedto any type of polymeric foam (e.g., ETHAFOAM*, STYROFOAM*, latex foams,etc.) or polymer sheet (e.g., polyethylene, polypropylene, polyurethane,ABS, polycarbonate, etc.). The areas of utilization of this inventioninclude automotive seating and door panels, laminating mattress coversto mattress foam, furniture upholstery, pillows, wall coverings,acoustic insulation, camera bags, video recorder cases, other padded orprotective enclosures, and the like.

Currently, special additives (e.g., PVC, polyester, SARAN* polymer,metal filings, low molecular weight "doping agents", etc.), which impartdielectric heatability to the polyurethane flexible foam, are used inthe foam formulation in order to obtain the advantages of dielectriclamination and embossing (i.e., speed, energy efficiency,non-destructive to the remainder of the foam, and simultaneouslyembossing). These special foam formulations require special processingequipment, and generally result in a foam which does not have optinumphysical properties (i.e., the additive decreases the percent opencells, decreases the percent elongation, increases the "boardiness" ofthe foam, and decreases resistance to moisture and heat). In addition,the arc resistance of the foam produced must be carefully adjusted orcontrolled in order to provide a seal without burning through thelaminate when varied thicknesses are made. One method of overcoming theneed for special formulations has been through the utilization of avinyl plastisol, which has been painted onto the urethane foam structureand is dried to "cure". This method is also expensive, requiring anadded production step and a major amount of plastisol is required sinceurethane foams are open celled and act as a sponge. Due to the addedcost, difficulties in production and increased number of productionsteps, the use of dielectric lamination and embossing has beenrestricted to specialty applications, such as automotive upholstery,which can tolerate the above disadvantages.

Our presently claimed invention pertains to the dielectric lamination offabric to foam without any of the above disadvantages. In addition, thedielectrically sealable polyolefin film beneficially acts as a waterbarrier (i.e., efficiently seals the foam, preventing water absorption)unless a film is used which is porous enough to allow the foam laminateto "breathe". The invention is extremely versatile in that it allowslaminates of any type fabric or other covering material to be laminatedto any type of polymeric foam or sheet.

The following examples were made utilizing a commercially availableCallanan 1.5 KW, Model 15 dielectric sealing unit operated at ˜30 MHz.The unit is equipped with the standard electronic sealing pressutilizing an electrode which results in a 1/8"×12" (1"=2.54 cm) seal.

EXAMPLE 7

A 4"×4"×1/2" sheet of slabstock of polyurethane foam, a 4"×4"×0.0015"piece of blown film of an ethylene/acrylic acid/carbon monoxide (EAACO)interpolymer (5% by weight acrylic acid, 10% by weight carbon monoxideand a 6 melt index), and a 4"×4" piece of polyester fabric were placedbetween the electrodes of the dielectric sealing unit. The sealer wasset at 100% power, a 2-second lamination time, a 2-second hold time, and60 psi clamp pressure. The composite was sealed utilizing the abovesettings and the resulting laminate had an interlayer bond strengthgreater than the tear strength of the foam. In other words, the bondfailure was cohesive failure of the foam rather than adhesive failure atthe bond.

EXAMPLE 7-A Comparative Example

The same procedure was followed as detailed in example 7 except that theEAACO film was not used. After the sealing effort, no seal was observedbetween the foam and the fabric.

EXAMPLE 7-B Comparative Example

The same procedure was followed as detailed in example 7 except theEAACO film was replaced with a film of ethylene/acrylic acid (EAA)interpolymer (9% by weight acrylic acid, 9 melt index). After thesealing effort, no seal was observed between the foam and the fabric.

EXAMPLE 7-C Comparative Example

The same procedure was followed as detailed in example 7 except theEAACO film was replaced with a film of LDPE (low density polyethylene,0.925 density, 2 melt index). After the sealing effort, no seal wasobserved between the foam and the fabric.

EXAMPLE 7-D

The same procedure was followed as detailed in example 7 except theEAACO film was replaced with a 3 mil thick film of ethylene/carbonmonoxide interpolymer (ECO) (10% by weight carbon monoxide at a 1 meltindex). After sealing, the laminate seal had an interlayer bond strengthgreater than the tear strength of the foam.

EXAMPLE 8

The same procedure was followed as detailed in example 7 except theEAACO film was replaced with a 3 mil thick film of ethylene/vinylacetate interpolymer (EVA) (18% by weight vinyl acetate at a 3.5 meltindex). After sealing, the laminate seal had an interlayer bond strengthless than the tear strength of the foam, but had sufficient adhesion tolaminate the fabric to the foam.

EXAMPLE 9

The same procedure was followed as detailed in example 7 except theurethane foam was replaced with a 4"×4"×1/4" piece of ETHAFOAM* polymer(a polyethylene foam available from The Dow Chemical Company) and theEAACO film was replaced with a film of ECO copolymer. The laminationtime was 4 seconds and hold time was 6 seconds. After sealing, thelaminate had an interlayer bond strength greater than the tear strengthof the foam.

The main distinguishing component of our presently claimed invention isthe dielectrically sealable polyolefin film. The film must not only bedielectrically sealable, but also should have adhesion to the desiredsubstrates (i.e., fabric or coating, and the foam). The ability of apolymer to undergo dielectric heating, or to accept high frequencyenergy is perhaps best explained by the previously described equation.

E' tan δ is called the loss index and is a relative measure of thepolymer's ease of heating. In general, the following table ranks theease of heating of a polymer utilizing high frequency electromagneticradiation.

    ______________________________________                                        Loss Index          Heatability                                               ______________________________________                                        ≧.2          Excellent                                                 .07-.2              Good                                                      .01-.07             Poor                                                      ≦.01         No Response                                               ______________________________________                                    

The lower the loss index of a polymer, the higher must be the voltageand/or frequency (note that the loss index is an unpredictable functionof frequency) in order to obtain the required heating rate. Thus, onewishes to use the polymer with the highest loss index possible which hasthe necessary adhesion and strength characteristics required for thedesired lamination. The following table presents the loss indices ofpolyolefins which are felt to be part of this invention (i.e., allpolyolefin films which have a loss index greater than 0.01) as well ascomparative examples.

    ______________________________________                                        Polymer           Dielectric Loss Index                                       ______________________________________                                        ECO.sup.2 - 10% CO                                                                              .074                                                        ECO.sup.2 - 5% CO .041                                                        ECO - 22% CO      .28                                                         EAACO.sup.3 - 5% AA, 5% CO                                                                      .054                                                        EAACO - 5% AA, 10% CO                                                                           .087                                                        EVA.sup.4 - 7.5% VA                                                                             .030                                                        EVA - 28% VA      .16                                                         EVACO.sup.5 - Elvaloy 741                                                                       .39                                                         EAA.sup.6 - 10% AA                                                                              .0036                                                       EAA - about 20%   .0059                                                       LDPE.sup.7        .0008                                                       ______________________________________                                         .sup.1 Measured utilizing ASTM D1531 at 1 MHz at 20° C.                .sup.2 Ethylene/carbon monoxide                                               .sup.3 Ethylene/acrylic acid/carbon monoxide                                  .sup.4 Ethylene/vinyl acetate                                                 .sup.5 Ethylene/vinyl acetate/carbon monoxide                                 .sup.6 Ethylene/acrylic acid                                                  .sup.7 Low density polyethylene (LDPE)                                   

With respect to the presently claimed invention the dielectric lossindex of the polymer film should be greater than 0.01 and preferablygreater than 0.08. The required film thickness will be dependent on thetype and characteristics of the materials to be laminated and empossed.The typical film thickness will range between 1.5 mils and 9 mils. Thefrequency of the dielectric sealer should range from 0.1 to 300 MHz andpreferably should range from 10 to 100 MHz. Microwave sealing is alsopossible, and sometimes preferred, utilizing frequencies from 300 to10,000 MHz.

Other polymeric films (not restricted to polyolefins) which have adielectric loss index greater than 0.01 are, e.g., nylon and SARAN*polymer, chlorinated P.E., polyesters, metal filled polymeric films,carbon black filled polymers, and the like.

Films of blends of high dielectric loss index polymers with low lossindex polymers are also operable if the loss index of the blend isgreater than 0.01. Polymer films to which an inorganic filler, whichmodifies the dielectric loss index of the composite, has been added andblended with a high dielectric loss polymer are also operable.

Currently, the automotive industry utilizes dielectric laminationtechniques for the fabrication of seat covers and door side panels. Thetechnology for the utilization of this invention is available for theabove application. Thus, the invention can be utilized by the automotiveindustry with the current lamination and embossing technology.

The utilities of this presently claimed invention include: thelamination of porous articles, e.g. non-woven fibers, to foam for use intextiles and the like; lamination of fabric and/or plastic sheeting tofoam for use in upholstery applications and the like; laminating a waterbarrier film or surface layer to foam in order to make water resistantfurniture or other articles or to act as a water barrier for foamproducts, e.g., foam insulation; and the lamination of two types orpieces of fabric together for use in textiles or similar articles.

The dielectrically sealable polymer film is inserted between the foamand the fabric covering or other covering, or can be prelaminated orextrusion coated to either the covering or the foam before the totalstructure is dielectrically laminated and embossed.

We claim:
 1. A composite article comprising a polymer foam havingHF-bonded thereto at least one surface layer, wherein the HF-bonding iseffected by a layer of HF-bondable polymer film between said foam andsaid surface layer, said HF-bondable polymer film comprising a carbonmonoxide-containing olefin interpolymer having a dielectric loss indexof about 0.01 or greater,said polymer foam being selected from the groupconsisting of foamed olefin polymers, polystyrene foam, polycarbonatefoam, latex foam, rubber foam, foamed ABS polymer, foamed PVC, formedPVDC, foamed acrylates, foamed methacrylates, foamed styrenic/olefiniccopolymers, and foamed polymer blends.
 2. The article of claim 1 whereinthe surface layer is selected from the group comprising polymers,fabrics, leather, cellulosic products, wood, vitreous material, metalfoils, paper, and foams.
 3. The article of claim 1 wherein theHF-bondable polymer film comprises a carbon monoxide-containing olefininterpolymer having a dielectric loss index of 0.02 or greater alloyed,blended, or otherwise admixed with a heat-plastifiable polymer having adielectric loss index of less than 0.01 in an amount such that thecombination has a dielectric loss index of 0.01 or greater.
 4. Thearticle of claim 1 wherein the HF-bondable polymer film comprises atleast one of ECO, ECOAA, ECOMAA, and ECOVA.
 5. The article of claim 1wherein the HF-bondable polymer film is bondable at MW-frequencies.
 6. Amethod of making laminated foam article, said method comprising placinga layer of HF-bondable polymer film between a polymer foam layer, otherthan polyurethane foam, and a surface layer, holding the layers closelytogether, and subjecting the layers to HF frequency radiation, in thearea where bonding is desired, for a time sufficient to melt orheat-plastify the HF-bondable polymer film, after which time the layersare cooled, thereby effecting bonding,wherein the HF-bondable polymerfilm comprises a carbon monoxide-containing olefin interpolymer.
 7. Themethod of claim 6 wherein the polymer foam is at least one selected fromthe group comprising foamed olefin polymers, polystyrene foam, epoxyfoam, polycarbonate foam, latex foam, foamed rubber, foamed ABS polymer,foamed PVC, foamed PVDC, foamed acrylates, foamed methacrylates, foamedstyrenic/olefinic copolymers, and foamed polymer blends.
 8. A method ofclaim 6 wherein the surface layer is selected from the group comprisingpolymers, fabrics, leather, cellulosic products, wood, metal foils,paper, and polymer foams.
 9. The method of claim 6 wherein theHF-bondable polymer film comprises a carbon monoxide-containing olefininterpolymer having a dielectric loss index of 0.02 or greater alloyed,blended, or otherwise admixed with a heat-plastifiable polymer having adielectric loss index of less than 0.01 in an amount such that thecombination has a dielectric loss index of 0.01 or greater.
 10. Themethod of claim 6 wherein the HF-bondable polymer film comprises atleast one of ECO, ECOAA, ECOMAA and, ECOVA.
 11. A laminated structuremade in accordance with claim 6.